Modeling Water and Nitrogen Balance of Different Cropping Systems in the North China Plain

Abstract

The North China Plain (NCP) is experiencing serious groundwater level decline and groundwater nitrate contamination due to excessive water pumping and application of nitrogen (N) fertilizer. In this study, grain yield, water and N use efficiencies under different cropping systems including two harvests in 1 year (winter wheat-summer maize) based on farmer (2H1Y) FP and optimized practices (2H1Y) OPT , three harvests in 2 years (winter wheat-summer maize-spring maize, 3H2Y), and one harvest in 1 year (spring maize, 1H1Y) were evaluated using the water-heat-carbon-nitrogen simulator (WHCNS) model. The 2H1Y FP system was maintained with 100% irrigation and fertilizer, while crop water requirement and N demand for other cropping systems were optimized and managed by soil testing. In addition, a scenario analysis was also performed under the interaction of linearly increasing and decreasing N rates, and irrigation levels.Results showed that the model performed well with simulated soil water content, soil N concentration, leaf area index, dry matter, and grain yield. Statistically acceptable ranges of root mean square error, Nash-Sutcliffe model efficiency, index of agreement values close to 1, and strong correlation coefficients existed between simulated and observed values. We concluded that replacing the prevalent 2H1Y FP with 1H1Y would be ecofriendly at the cost of some grain yield decline. This cropping system had the highest average water use (2.1 kg m −3 ) and N use efficiencies (4.8 kg kg -1 ) on reduced water (56.64%) and N (81.36%) inputs than 2H1Y FP . Whereas 3H2Y showed insignificant results in terms of grain yield, and 2H1Y FP was unsustainable. The 2H1Y FP system consumed a total of 745 mm irrigation and 1100 kg N ha -1 in two years. When farming practices were optimized for two harvests in 1 year system (2H1Y) OPT , then grain yield improved and water (18.12%) plus N (61.82%) consumptions were minimized. There was an ample amount of N saved, but water conservation was still unsatisfactory. However, considering the results of scenario analyses, it is recommended that winter wheat would be cultivated at <200 mm irrigation by reducing one irrigation event.Since the 1970s, the annual use of the two-harvest cropping system greatly increased the total grain output. However, it has also caused severe groundwater decline [7,8], because both crops generally have high water requirements to complete their life cycle [9,10]. Crop water requirement does not meet the balance between groundwater recharge through rain and evapotranspiration (ET) loss from plant and soil [11]. An estimated amount of more than 450 mm yr −1 irrigation water is required to maintain high crop yield under the conventional double cropping system [12], which dominatingly depends on pumping of groundwater, and there is no access to irrigation from the river source. Thus, the groundwater is almost the only source of irrigation [13]. In the last 20 years, sustained water pumping has adversely affected aquifers. Consequently, the groundwater leve...

Impact of Tillage and Residue Management on Hydro-physical Properties of Clay Soil under Rice-wheat Cropping System in Indo-Gangetic Plains of India

“…A field experiment was conducted during 2010-2012 to study the residual impact of tillage and residues under the paddy-wheat cropping system with wheat as a test crop (Tables 1 and 2 Ploughing twice by cultivator, allowed to decompose weeds for a week then puddling by cross ploughing and planking T 3 Summer ploughing onset of monsoon by mould board plough to invert the soil once in three years followed by subsequent ploughing by cultivator to puddle the soil. T 4 Disc ploughing once in three years after the onset of monsoon to invert the soil.…”

“…Because of deteriorating, physical and hydraulic properties, and low organic carbon content of the soil under increasing intensification, the present productivity potential of the rice-wheat cropping system in this region is under threat. With decreasing per capita land area (currently <0.1 ha), the risk of degradation has greatly increased, posing a severe challenge to soil management for resource conservation, especially sustainable soil use [1,2,3].…”

Sustainable Cropping Systems

“…Declining aquifer levels are a serious threat to crop production in semi-arid and arid areas that rely on them for irrigation. The article by Leghari et al [56] uses data from the North China Plain and simulation modeling to assess crop productivity and water and N use efficiencies for the predominant winter wheat-summer maize double-crop system under standard and optimized rates of irrigation and N, and for monocropped spring maize and a two-year winter wheat-summer maize-spring maize rotation under optimized irrigation and N rates. Across the two study years, the double-cropped system under optimized irrigation and N rates produced the greatest total grain yield, which was 6% greater than that of the same system when 22% more water and 162% more N were applied.…”

Exploring a Sustainable Cropping System in the North China Plain Using a Modelling Approach

“…A fallow period from October to the following April is then observed. However, the NCP has a typical monsoonal climate with 70% to 80% of annual rainfall concentrated from June to September, thus overlapping with the growing season of maize [4,11]. Given these climate characteristics, a high amount of irrigation water is essential for WW production [12,13].…”